In designing a mailing system used to create mail pieces, each mailing piece consisting of mail pages inserted in an envelope, throughput with reliability is always an objective. To achieve reliability it is sometimes advantageous to provide parallel paths, each path operating at a lower throughput than the desired overall throughput so that mail piece components do not change velocity so quickly as to be damaged or to jam in the mailing system.
Many mailing systems include insertion engines, which insert mail pages into an envelope (after the mail pages are folded, if necessary). In some mailing systems with an insertion engine, throughputs as high as 18,000 mail pieces per hour (five per second) are achieved. In such a mailing system, an insertion engine is provided with the envelopes of the mail pieces by an envelope transport system (and is provided with the pages of the mail pieces, to be inserted into the envelopes, by a page transport system).
The envelope transport system includes an envelope hopper (12 of FIG. 1) that must be periodically loaded with envelopes. In some mailing systems, because of various constraints, it is necessary that the envelope hopper be on the same side of the mailing system as where the operator is stationed, and of course that the envelope hopper be easily loadable. An envelope hopper typically holds about 1500 envelopes when fully loaded, and so must be replenished about every five minutes when used in a mailing system operating at a throughput of five mail pieces per second.
In some mailing system architectures, all of these requirements combine so that a layout of the envelope transport system can use a planar envelope hopper (12 of FIG. 1) feeding envelopes (11 of FIG. 1) on edge. In such a situation, what is needed is a design for an envelope transport system that allows using such a feeder, and that provides envelopes at the required high throughput, but that keeps changes in the envelope velocity to within acceptable limits.